The present invention relates to a panel member for the underside of a vehicle, and more particularly to a panel member for the underside of a passenger car.
Panel members typically are fitted along the underside of an automobile and held in a spaced relation from the ground, or roadway, by the wheels of the vehicle. A panel member can have an aerodynamically designed shape in certain areas and can include one or more constricted portions. As used herein, a constricted portion relates to a portion of the panel member which extends downwardly from the underside of the panel member, relative to other portions of the panel member. A downwardly extending constricted portion thus forms a constricted space between the ground and the underside of the vehicle, relative to other portions of the panel member.
One conventional panel member is described in U.S. Pat. No. 3,776,587. This panel member includes one convex curved portion which is disposed behind the front axle and another convex curved portion disposed in the general vicinity of the rear axle. These convex curved portions form venturi pipe-like constrictions between the panel member and the ground or roadway. Experiments have shown that the placement of a constricted portion behind the front axle adversely affects the drag coefficient and the negative lift at the front axle. Additionally, it has been found that a constricted portion underneath the rear axle of a vehicle causes a positive lift which can substantially impair driving safety.
It is an object of the present invention to provide a panel member for the underside of an automotive vehicle which improves the drag coefficient of the vehicle and provides good negative lift at the front and rear axles. By providing good negative lift at the front and rear axles, the road-hugging ability of the car is enhanced.
In accordance with the instant invention, a panel member arrangement is provided for a motor vehicle having an upper side, an underside, front wheels, and rear wheels. The panel member arrangement comprises a panel member which can be disposed on the underside of the vehicle to cover parts of the chassis such as the axles, and which can be supported by the motor vehicle's wheels above the ground in a spaced relation to the ground. The panel member includes a central portion and a first constricted portion. The first constricted portion is disposed in front of the front wheels of the motor vehicle, and provides a first constricted space between the panel member and the ground. The second constricted portion is disposed behind the rear wheels of the vehicle to provide a second constricted space between the panel member and the ground. First and second boundary element portions are disposed along the sides of the panel member for forming an air duct with the central portion.
Preferably, the panel member includes first and second front wheel cut-out portions and first and second concavely shaped ascending ramp portions. The ascending ramp portions are disposed along the sides of the panel member in front of the front wheel cut-out portions. The ascending ramp portions each include a forward portion adjacent the front of the panel member and a rearward portion. The rearward portions are disposed adjacent the respective front wheel cut-out portions, and are generally as wide as the front wheels of the vehicle. The ascending ramp portions each extend downwardly and rearwardly from the front of the panel member to the respective front wheel cut-out portions.
One advantage of the present invention is that the drag coefficient of the vehicle is substantially improved due to the arrangement and configuration of the constricted portions, the contoured section of the smooth-surfaced panel member and the air ducts. This improvement is effected while retaining a negative lift which enhances the road-hugging ability of the vehicle.
One advantageous feature of certain preferred embodiments of the present invention is that a concave leading section is provided in front of the first constricted portion. This feature has the advantage of directing an air stream to the first constricted portion in a a controlled fashion.
It is also an advantageous feature of certain preferred embodiments of the present invention that convex ascending ramps are provided in front of the front wheels of the vehicle. The convex ascending ramps have the advantage of conducting the air flow past the front wheels.
Another advantageous feature of certain preferred embodiments of the present invention is that the first constricted portion is provided with a concave trailing section. This feature has the advantage of effecting a reduction in air resistance and promotes good negative lift at the front axle according to the venturi principle.
One advantageous aspect of the present invention is that boundary element portions are provided which extend along the sides of the panel members between the front and rear wheels. The boundary element portions effect the channeling of the air flow in the bottom panel zones, and help to avoid eddies between the wheels. These eddies tend to raise air resistance, and hence increase the drag coefficient of the vehicle. Additionally, these boundary elements prevent the influx of air into the vacuum region underneath the vehicle. Preferably, the boundary elements are each provided with a rounded leading section and a rounded trailing section. The rounded leading and trailing sections produce an improved air flow in the bottom panel regions and serve to guide the air flow past the rear wheels to lower the incidences of eddies.
In a preferred embodiment of the present invention, the second constricted portion is provided with a concave leading section and a convex trailing section. The concave leading section provides a negative lift at the rear axle, according to the venturi principle. The convex trailing section includes a rounded transition portion which provides a smooth transition between the generally horizontal panel member and a vertically oriented side wall of the vehicle, to provide good conductance of air toward the side of the vehicle. The convex trailing section also includes a sharp-edged transition portion between the trailing section and the rear end wall of the vehicle. This sharp-edged transition portion acts as a breakaway rim for air flow at the rear of the vehicle.
The trailing section behind the second constricted portion cooperates with a rear spoiler, which is disposed in the upper zone of the automotive vehicle, to provide a negative lift at the rear axle which is greater than the negative lift at the front axle. This greater negative lift at the rear axle increases driving safety by providing a slightly understeering driving characteristic to the vehicle at higher speeds.
Additionally, the panel member can include a countersunk duct for receiving the exhaust pipe of the vehicle. This hidden arrangement of the exhaust pipe in the duct reduces turbulence in the air flow along the underside of the vehicle.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.